核分裂

• Reading: かくぶんれつ
• Romaji: kakubunretsu
• Kanji breakdown: 核 (kaku) — nucleus, core; 分 (bun) — to divide; 裂 (retsu) — to split, to tear
• Pronunciation: /ka.kɯ.bɯɴ.ɾe.tsɯ/

Meaning

Nuclear fission; the splitting of a heavy atomic nucleus into lighter nuclei, releasing large amounts of energy.

A compound of 核 (nucleus) and 分裂 (splitting, division). Nuclear fission is the physical process underlying nuclear reactors and atomic bombs. In Japanese, 核分裂 is distinguished from 核融合 (nuclear fusion — the opposite process). The chain reaction (連鎖反応) in fission is central to both weapons design and reactor engineering. The term appears frequently in discussions of nuclear energy policy (原子力政策), radiation safety (放射線安全), and disarmament (軍縮).

Examples

1. ウランの核分裂によって放出される膨大なエネルギーが、原子力発電の原理となっている。 The enormous energy released by the fission of uranium is the principle behind nuclear power generation.
2. 核分裂の連鎖反応を制御することが、原子炉設計における最大の技術的課題だ。 Controlling the chain reaction of nuclear fission is the greatest technical challenge in reactor design.
3. 核分裂と核融合は、どちらも質量がエネルギーに変換される現象だが、そのメカニズムは異なる。 Both nuclear fission and nuclear fusion are phenomena in which mass is converted into energy, but their mechanisms differ.

Usage Guide

Context: nuclear physics, energy policy, chemistry, engineering, history of science

Tone: technical, neutral

Origin & History

Modern scientific compound: 核 (kaku) — nucleus + 分裂 (bunretsu) — splitting, division. Coined in Japan during the early nuclear age (1930s–40s) to render the physics concept of 'fission'. 分裂 itself is a classical Sino-Japanese word meaning 'to split apart'.

Cultural Context

Era: Modern

Generation: Adult

Social background: Educated